This invention relates generally to a blow molding method and apparatus and more particularly, it concerns an improved blow molding apparatus system for successively forming a plurality of thermoplastic articles.
Many devices have been proposed for the continuous forming of thermoplastic articles. These devices include such features as a turret having a vertical axis in order to enable the selective indexing of a plurality of sets of core pins into an injection mold. Such a feature enables the continuous forming of thermoplastic preforms between the core pins and the mold cavities of the injection mold.
While this feature facilitates the successive formation of preforms on core pins it does not directly address the problem of maximizing the number of preforms which might be formed on a given iteration or within a given time span. It also does not address the problem of cooling the preform sufficiently and within a minimum time frame such that the removal of the preforms may be accommodated without substantial deformation of the preform.
Previous blow molding apparatus have also included a preform mold which has a unibody construction into which the core pin is inserted and the preform is injection molded. This feature is undesirable because of the time period necessary for the preform to cool before removing the core pin and preform and because of the increased wall friction and suction created by the unibody construction upon removal of the core pin.
Additionally, once removed from the mold cavity, the preform has been allowed in the past to cool on the core pin or has been removed from the core pin and placed on a conveyor to be cooled. Oftentimes, when these alternatives are utilized, irregularities in the wall thickness greatly lengthen the amount of time necessary for complete cooling in that the time necessary for the cooling of the preform given such regularities is the time necessary for the maximum thickness to adequately cool.
Still other apparatus require several steps for the removal of the preform from the core pin, for the conveying of the preform through thermal conditioning, and for the spacing of the preform preparatory to blow molding. These additional steps require extra time and extra machinery, thereby increasing the cost of production per article.
Accordingly, in order to provide an improved blow molding apparatus, it is desirable to provide an apparatus which minimizes the cooling time of the peform on the core pin prior to its removal. The apparatus should maximize the number of preforms manufactured for each iteration while minimizing the cost and size of the machinery. Additionally, the device should maximize the efficiency with which the preforms are handled from removal to blow molding in order to minimize the time per unit and maximize the production thereby.